| Popis: |
Surface structure of muscovite was imaged using atomic force microscope (AFM) at contact rnode in water. The AFM image data obtained were interpreted by comparing with the bulk structure data of muscovite determined by the Rietveld refinement of X-ray powder diffraction data. Three types of AFM images were ebserved as follows：(1) showing clearly the arrangement of hexagonal rings of SiO4 tetrahedra, (2) showing a hexagonal array of bright spots separated by a distance of about 5.3 A, and (3) changing gradually from image (2) to image (1). The mean unit cell distances (a＝5.28±0.14A, b ：9.28±e.17A) for the muscovite surface with the image (1) are slightly longer than those (a＝5.202±0.002 A, b ：9.024±0.003A) of the bulk structure obtained by X-ray diffraction. This slight increase of the cell distances is likely caused by rehydrating in solution, of which H2O molecules entered into the siloxane rings and consequently expanded its surface structure. Further, image (1) provides the information of the tetrahedral tilt and basal surface cerrugation caused by the tetrahedral tilt. lmage (3), may be produced by a slight change in the tip-surface interaction during scanning, evidences that image (2) shows not the arrangement of interlayer K ions but the basal plane of the tetrahedral sheet. Some structural reiaxation of the tetrahedral sheet surface was also observed. ln the arrangement of hexagonal rings, some individual smaller hexagonal rings were randomly found. The outer hexagonal rings enlarge gradually with the distance from the smaller central hexagonal ring. This leads to a single-mode distribution of unit cell distances. |
